Battery apparatus for controlling plural batteries and control method of plural batteries

ABSTRACT

Lower order control devices control plural battery cells configuring plural battery modules. An input terminal of the low order control device in the highest potential, an output terminal of the low order control device in the lowest potential, and a high order control device are connected by isolating units, photocouplers. Diodes which prevent a discharge current of the battery cells in the battery modules are disposed between the output terminal of the low order control device and the battery cells in the battery module on the low potential side. Terminals related to input/output of a signal are electrically connected without isolating among the plural low order control devices.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a battery apparatus forcontrolling plural high energy battery cells connected in series and itscontrol method, and more particularly to a battery apparatus which issuitable for a low order control device which controls a battery modulehaving plural battery cells connected in series and a high order controldevice for giving instructions to plural low order control devices.

[0002] For example, Japanese Patent Laid-Open Publication No. 10-322925describes a conventional battery apparatus which is comprised of pluralbattery cells connected in series as a battery module, plural batterymodules being connected in series, and a low order control devicedisposed for each battery module, a command being sent from a high ordercontrol device to the low order control device. The low order controldevices monitor the states of the battery cells possessed by thecorresponding battery modules. The low order control devices disposed inthe same quantity as that of the battery modules are electricallyconnected in series via the battery modules, a signal is transmittedbetween the high order control device and the low order control devicesand between the low order control devices by an isolating unit such as aphotocoupler in a configuration that no affect is caused by a potentialdifference between the control devices.

[0003] The low order control device adjusts the capacity of the batterycells as described in Japanese Patent Laid-Open Publication No.2000-92732 for example. The capacity adjustment means the reduction of avoltage difference between the battery cells by having a resistorconnected in parallel to the battery cells via a switch, and when thebattery cells measured by a voltage detection circuit have a highvoltage, driving the switch to partly discharge the amount ofelectricity stored. Particularly, a lithium-ion battery, which hasamorphous carbon with high relevancy between an open-circuit voltage anda remaining capacity as an anode active material, can effectivelyequalize the capacity of each battery cell by reducing a voltagedifference between the battery cells.

[0004] In recent years, there has been used an ultra capacitor which canstore the same amount of electricity as the secondary battery and hasless degradation in service life as compared with the secondary battery.The ultra capacity adopts a method of equalizing the voltage between thecapacitor cells as described in Japanese Patent Laid-Open PublicationNo. 2001-37077 for example. This method provides a circuit whichconnects a switch in parallel to the capacitor cells to detect thevoltage of the capacitor and bypasses part of electricity to the switch.It is similar to the aforesaid Japanese Patent Laid-Open Publication No.2000-92732.

[0005] The low order control device detects a voltage of the batterycell or the capacitor cell, and when the voltage is high, operates theswitch to adjust the capacity. Meanwhile, the high order control devicesends an instruction signal to make the low order control device toadjust the capacity. In Japanese Patent Laid-Open Publication No.2000-92732, an open-circuit voltage of each battery cell of the batterymodule is measured when the low order control device is activated, andthe measured value is transmitted to the high order control device. Thehigh order control device calculates a reference voltage value at thetime of capacity adjustment from the value of open-circuit voltageobtained from all the low order control devices and gives instructionsto the low order control devices again.

SUMMARY OF THE INVENTION

[0006] Problems to be remedied by the present invention are followingthree. First, it is a cost problem. The secondary battery and the ultracapacitor are expected to be used for a battery apparatus for theelectric car or the hybrid electric car, but it is demanded that theircosts are reduced for mass production. For the cost reduction of thebattery apparatus, it is necessary to reduce the cost of the batterycell or the capacitor cell itself and also to reduce the costs of theplural low order control devices. To achieve it, it is effective to havethe low order control devices as ICs (integrated circuits).

[0007] However, even when the low order control device is ICed, theisolating unit such as a photocoupler used for the signal transmissionbetween the high order control device and the low order control devicesand between the low order control devices remains as it is. For example,when a lithium-ion battery is used, it is assumed that the battery cellhas a voltage of 3.6V and 40 batteries are connected in series, thispotential difference is 144 V between the battery in the lowestpotential and the battery in the highest potential. In this example, iffour battery cells are grouped into each battery module, ten low ordercontrol devices are provided, and the respective low order controldevices are provided with about two isolating units for input andoutput. Thus, a total of 20 isolating units are necessary, and there isa disadvantage that the control devices cost high.

[0008] Second, there is a problem of reliability. There is a possibilitythat an external interference enters the instruction signal due to noiseproduced by an inverter device or the like which is connected as a loadon the battery apparatus. Therefore, there is a problem that thereliability of the signal transmission is decreased when instructionsare given from the high order control device to the low order controldevices because of the external interference.

[0009] Third, there is a problem of accuracy of detecting a voltage. Theplural low order control devices are provided with a voltage detectioncircuit and detect a voltage of the battery cells disposed in thecorresponding battery modules, but the battery voltage detection needshighly accurate performance with merely an allowable error of severaltens of mV. A lithium-ion battery, which uses amorphous carbon for theanode active material, has an obvious relation between the open-circuitvoltage and the remaining capacity as compared with another battery suchas a nickel metal hydride battery. But, it is said that even thelithium-ion battery has an allowable error of ±50 mV or less in voltageequalization for the capacity adjustment. Conversion of a voltage of 50mV is equivalent to about 5% of the remaining capacity of thelithium-ion battery. The highest voltage of the lithium-ion battery isabout 4.2V but the aforementioned 50 mV is 1.2% with respect to 4.2%,indicating that the accuracy of voltage detection is very strict.

[0010] In order to achieve the highly accurate voltage detection, an A/Dconverter of ten-odd bits is generally used, but the accuracy of the A/Dconverter depends on the accuracy of a reference voltage source.Therefore, the low order control device needs a highly accuratereference voltage source with an extremely small error (e.g., about ±25mV). Since each low order control device is connected to the batterymodule having a different potential, it is difficult to share the highlyaccurate reference voltage source with the plural low order controldevices. Specifically, to achieve the highly accurate voltage detection,there was a problem that the cost of the reference voltage sources whichare respectively provided for the plural low order control devicesbecame high.

[0011] A first object of the present invention is to provide a batteryapparatus which has a quantity of isolating units decreased and isprovided with low-cost control devices.

[0012] A second object of the invention is to provide a control methodof a battery apparatus, which reduces the influence by externalinterferences such as noise and can make the signal transmission withimproved reliability.

[0013] A third object of the invention is to provide an inexpensivebattery apparatus which can achieve the highly accurate voltagedetection.

[0014] (1) In order to achieve the first object, the invention isdirected to a battery apparatus comprising plural battery modulesconnected in series which have plural battery cells connected in series;plural low order control devices which are disposed in correspondencewith the plural battery modules and control the plural battery cellsconfiguring the battery modules; and a high order control device whichcontrols the plural low order control devices, wherein there areprovided an isolating unit or a potential converting unit which connectsthe input terminal of the low order control device in the highestpotential among the plural low order control devices, the outputterminal of the low order control device in the lowest potential, andthe high order control device; and an interruption element which isdisposed between the output terminal of the low order control device andthe battery cells in the battery module on a low potential side andprevents the discharge current of the battery cells in the batterymodule; and terminals related to the input and output of a signal areelectrically connected in a non-isolated state among the plural loworder control devices.

[0015] By configuring as described above, the quantity of the isolatingunits can be reduced, and the low-cost control device can be obtained.

[0016] (2) In the item (1) above, it is preferable that the inputterminal of the low order control device is electrically connected tothe battery cell on a high potential side among the battery cells withinthe battery module being controlled by the low order control device.

[0017] (3) In the item (2) above, it is preferable that the plural loworder control devices, the isolating unit or the potential conversionunit which is disposed on the low order control devices in the highestand lowest potentials, and the high order control device are mounted onthe same package, and power is supplied from the outside of the packageto the high order control device.

[0018] (4) To achieve the first object, the invention is directed to acontrol method of battery cells which is provided with plural batterymodules connected in series which have plural battery cells connected inseries; plural low order control devices which are disposed incorrespondence with the plural battery modules and control the pluralbattery cells configuring the battery modules; and a high order controldevice which controls the plural low order control devices, wherein thehigh order control device compares a signal transmitted to the low ordercontrol device in the highest potential with a signal returning from thelow order control device in the lowest potential, and transmits the nextinstruction when it is determined to be normal.

[0019] The aforementioned method enables to improve the reliability byreducing an influence due to the external interference such as noise.

[0020] (5) In the item (4), it is preferable that the low order controldevice detects the states of the plural battery cells of the batterymodule controlled by the low order control device, takes a logical addor a logical product of the state detection signal and an input signaltransmitted from the low order control device in a high potential, andoutputs the result to the low order control device in a low potential;and the high order control device determines a defect of the batteryapparatus according to the signal returning from the low order controldevice in the lowest potential.

[0021] (6) In the item (4), it is preferable that the low order controldevice performs the capacity adjustment to discharge the remainingcapacity of the battery cell when the voltage of the battery cells inthe battery module is higher than a reference value, and the low ordercontrol device having completed the capacity adjustment gets into asleep mode.

[0022] (7) To achieve the third object, the invention is directed to abattery apparatus, comprising plural battery modules connected in serieswhich have plural battery cells connected in series; plural low ordercontrol devices which are disposed in correspondence with the pluralbattery modules and control the plural battery cells configuring thebattery modules; and a high order control device which controls theplural low order control devices, wherein there are provided a voltagedetecting unit which detects a voltage of the plural battery cellswithin the battery modules, and an error calibration terminal whichcalibrates an error of the voltage detecting unit.

[0023] By configuring as described above, the highly accurate voltagedetection can be achieved, and the cost reduction can also be achieved.

[0024] (8) In the item (7), it is preferable that the voltage detectingunit is an A/D converter, and the low order control device compensatesan output value by previously giving a digital value to the errorcalibration terminal of the A/D converter.

[0025] (9) In the item (8), it is preferable that the A/D convertercomprises an integration unit which integrates a unit amount ofelectricity according to the number of pulses; a comparing unit whichcompares the integral value of the integration unit with the voltage ofthe battery cell and stops the pulse; a counter unit which outputs thenumber of pulses when the pulse is stopped by the comparing unit; and acompensation unit which compensates output of the counter unit accordingto the digital value given to the terminal for calibrating the error.

[0026] (10) In the item (9), it is preferable that the compensation unitchanges a counted value of the counter unit according to the digitalvalue given to the error calibration terminal to compensate an offset ofthe A/D conversion and changes a width of the pulse to compensate a gainof the A/D conversion.

[0027] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a circuit diagram showing a general structure of abattery apparatus according to one embodiment of the present invention;

[0029]FIG. 2 is a circuit diagram showing an internal structure of thelow order control device used for the battery apparatus according to oneembodiment of the invention;

[0030]FIG. 3 is a circuit diagram showing a first structure example ofan output circuit 6 and an input circuit 4 used for the low ordercontrol device in the battery apparatus according to one embodiment ofthe invention;

[0031]FIG. 4 is a circuit diagram showing a second structure example ofthe output circuit 6 and the input circuit 4 used for the low ordercontrol device in the battery apparatus according to one embodiment ofthe invention;

[0032]FIG. 5 is a flow chart showing the contents of control of thebattery apparatus according to one embodiment of the invention;

[0033]FIG. 6 is a flow chart showing the contents of control to adjustthe capacity in the battery apparatus according to one embodiment of theinvention;

[0034]FIG. 7 is a circuit diagram showing a structure of an A/Dconverter used in the battery apparatus according to one embodiment ofthe invention;

[0035]FIGS. 8A to 8D are timing charts of the A/D converter used in thebattery apparatus according to one embodiment of the invention;

[0036]FIG. 9 is a circuit diagram showing a structure of a first counter9 and a second counter 10 in the A/D converter used in the batteryapparatus according to one embodiment of the invention;

[0037]FIG. 10 is a truth table of the A/D converter used in the batteryapparatus according to one embodiment of the invention;

[0038]FIG. 11 is a circuit diagram showing a general structure of thebattery apparatus according to another embodiment of the presentinvention; and

[0039]FIGS. 12A to 12D are timing charts showing the contents of controlof the battery apparatus according to another embodiment of theinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The battery apparatus and its control method according to oneembodiment of the invention will be described with reference to FIG. 1to FIG. 10.

[0041] First, a general structure of the battery apparatus according tothis embodiment will be described with reference to FIG. 1.

[0042]FIG. 1 is a circuit diagram showing the general structure of thebattery apparatus according to one embodiment of the invention.

[0043] Electric cells VB1, VB2, . . . , VB12 which are secondarybatteries are divided into battery modules each of which has fourbattery cells connected in series. A secondary battery apparatus usedfor an electric car or a hybrid electric car may be provided with tensto twenties of battery modules. But, this embodiment always has the samestructure even when many modules are connected in series, so that theexample of FIG. 1 shows a structure example having three battery modulesconnected in series.

[0044] In the shown example, a first battery module in the highestpotential consists of the battery cells VB1, . . . , VB4. Positive andnegative electrodes of the respective battery cells VB1, . . . , VB4 areconnected to terminals T1, T3, T5, T7, T9 possessed by a first low ordercontrol device IC-1, respectively. A capacity adjustment circuitcomprised of a resistor R1 and a switching element S1 is providedbetween the positive and negative electrodes of the battery cell VB1. Acontrol signal is input from a terminal T2 of the low order controldevice IC-1 to a gate terminal of the switching element S1. Similarly,capacity adjustment circuits comprised of a resistor R2 and a switchingelement S2, a resistor R3 and a switching element S3, and a resistor R4and a switching element S4 are provided between the positive andnegative electrodes of the battery cell VB2, the battery cell VB3 andthe battery cell VB4, respectively. The gate terminals of the switchingelements S2, S3 and S4 input a control signal from terminals T4, T6, T8of the low order control device IC-1, respectively.

[0045] A second battery module in the middle potential is provided withthe battery cells VB5, . . . , VB8. Similar to the first battery module,positive and negative electrodes of battery cells VB5, . . . , VB8 arerespectively connected to terminals T1, T3, T5, T7, T9 possessed by asecond low order control device IC-2. The battery cells VB5, . . . , VB8are also provided with a capacity adjustment circuit, which has aresistor R5 and a switching element S5, a resistor R6 and a switchingelement S6, a resistor R7 and a switching element S7, and a resistor R8and a switching element S8 connected in series between the positive andnegative electrodes.

[0046] Similarly, a third battery module in the lowest potential isprovided with the battery cells VB9, . . . , VB12. Positive and negativeelectrodes of the battery cells VB9, . . . , VB12 are respectivelyconnected to terminals T1, T3, T5, T7, T9 possessed by a third low ordercontrol device IC-3. The battery cells VB9, . . . , VB12 are alsoprovided with a capacity adjustment circuit, which has a resistor R9 anda switching element S9, a resistor R10 and a switching element S10, aresistor R11 and a switching element S11, and a resistor R12 and aswitching element S12 connected in series between the positive andnegative electrodes. And, the respective switching elements are drivenby the third low order control device IC-3.

[0047] The internal structures, functions and peripheral parts of thelow order control devices IC-1, IC-2, IC-3 will be described later withreference to FIG. 2 and later figures.

[0048] Then, connected relations of the low order control devices IC-1,IC-2, IC-3 will be described.

[0049] As the battery cell BV4 and the battery cell VB5 are connected inseries, the first low order control device IC-1 and the second low ordercontrol device IC-2 are connected in series. Similarly, the second loworder control device IC-2 and the third low order control device IC-3are connected in series.

[0050] The high order control device MPU gives a command from the firstlow order control device IC-1 to the third low order control deviceIC-3. A control command output from the high order control device MPU isisolated by photocouplers F1, F2, F3 and transmitted to input terminalsIn-1, In-2, In-3 of the first low order control device IC-1. Lightreceiving side transistors of the photocouplers F1, F2, F3 arerespectively connected to resistors RF1, RF2, RF3. The resistors RF1,RF2, RF3 receive power from the positive electrode of the battery cellVB1. The first low order control device IC-1 outputs the signalstransmitted to the input terminals In-1, In-2, In-3 from outputterminals Out-1, Out-2, Out-3. The output terminal Out-1, the outputterminal Out-2 and the output terminal Out-3 are connected withoutelectrical isolation to input terminals In-1, In-2, In-3 possessed bythe second low order control device IC-2.

[0051] Similarly, the second low order control device IC-2 outputs thesignals transmitted to the input terminals In-1, In-2, In-3 from theoutput terminals Out-1, Out-2, Out-3. The output terminals Out-1, Out-2,Out-3 of the second low order control device IC-2 are connected withoutelectrical isolation to input terminals In-1, In-2, In-3 possessed bythe third low order control device IC-3.

[0052] The low order control device IC-3 in the lowest potentialoperates corresponding transistors Tr1, Tr2, Tr3 by the signals outputfrom the output terminals Out-1, Out-2, Out-3, and the respectivetransistors transmit the signals to the high order control device MPUvia photocouplers F4, F5, F6 to which the second low order controldevice is connected. Here, the light emitting sides of the photocouplersF4, F5, F6 are connected to a reference voltage output terminal VDD ofthe low order control device IC-3 to receive an electric current fromthe reference voltage output terminal VDD. Resistors RF4, RF5, RF6disposed between the light emitting sides of the photocouplers F4, F5,F6 and the transistors Tr1, Tr2, Tr3 are used to adjust an electriccurrent passing to the light emitting sides of the photocouplers F4, F5,F6.

[0053] The internal circuit of the low order control device IC-1 has thenegative electrode of the battery cell VB4 as a reference potential, andthis reference potential is indicated by GND-1. The internal circuits ofthe low order control device IC-2 and the low order control device IC-3have the negative electrodes of the battery cell VB8 and the batterycell VB12 as reference potentials, and these reference potentials areindicated by GND-2 and GND-3. The respective reference potentials GND-1,. . . , GND-3 are different ground terminals used for the correspondinglow order control devices IC-1, . . . , IC-3. Meanwhile, the ground inthe whole structure shown in FIG. 1 is assumed to be the negativeelectrode of a power supply Vcc for the high order control device MPU.The high order control device MPU and the low order control devicesIC-1, . . . , IC-3 are isolated by the photocouplers F1, . . . , F6, sothat the negative electrode of the Vcc is also isolated from therespective reference potentials GND-1, . . . , GND-3.

[0054] The terminals and peripheral parts of the low order controldevices IC-1, . . . , IC-3 will be described with reference to FIG. 2,but differences among the respective control devices IC-1, . . . , IC-3are potentials of the terminals A1, . . . , A3 and terminals B1, B2provided for them. These terminals are to compensate an error indetecting a voltage to be described with reference to FIG. 7, and adigital value “1” or “0” is given from the low order control device IC-1to the terminals A1, . . . , A3 and the terminals B1, B2 according tothe voltage detection error separately possessed by the low ordercontrol device IS-3. Here, “1” is a reference voltage VDD of the loworder control device, and “0” indicates potentials of the grounds GND-1,GND-2, GND-3 of the respective low order control devices. Theaforementioned voltage detection error is different among the low ordercontrol devices IC-1, . . . , IC-3, so that the value “1” or “0” of theterminals A1, . . . , A3 and the terminals B1, B2 is different among therespective low order control devices IC-1, . . . , IC-3 in the exampleof FIG. 1.

[0055] The high order control device MPU detects an electric current ofcharging and discharging passing to the battery module by an isolationtype current detector CT. To detect a total voltage value of the batterymodules connected in series, it is divided by resistors RV1, RV2. Here,the high order control device MPU and the respective battery modules areisolated from one another, so that the voltage divided by the resistorsRV1, RV2 is temporarily converted into a pulse signal by avoltage-frequency converter VF, and output of the VF is transmitted tothe high order control device MPU via a photocoupler F7. The high ordercontrol device MPU reads a total voltage of the battery modules from theoutput of the voltage-frequency converter VF obtained from thephotocoupler F7 and calculates an average remaining capacity of thethree battery modules based on the obtained value and the electriccurrent obtained from the current detector CT.

[0056] When the electric car or the hybrid electric car has tens totwenties of battery modules, a structure that the highest low ordercontrol device IC-1 and the lowest low order control device IC-3 areconnected via the high order control device MPU and the photocouplers isthe same as in FIG. 1. Remaining tens to twenties of the low ordercontrol devices which are disposed in the same number as the batterymodules are connected without isolation with the output terminal of thelow order control device having input terminals In-1, In-2, In-3disposed for a battery module in a potential higher by one level and theinput terminal of the low order control device having the outputterminals Out-1, Out-2, Out-3 disposed for a battery module in apotential lower by one level in the same way as the low order controldevice IC-2 of FIG. 1.

[0057] In the illustrated example, seven photocouplers F1, . . . , F6,F7 are used as isolating units. A configuration consisting of three loworder control devices IC-1, . . . , IC-3 is shown in the example of FIG.1, but even when there are ten low order control devices, the number ofphotocouplers as the isolating units may be seven. Meanwhile, accordingto a conventional configuration, when each battery module is comprisedof four battery cells and provided with ten low order control devices,each of the low order control devices is provided with about twoisolating units for input and output. Thus, a total of 20 isolatingunits are necessary. Meanwhile, because seven photocouplers are alwaysenough in this embodiment, the number of isolating units can bedecreased to reduce the cost of the control devices.

[0058] Then, an internal structure of the low order control device usedfor the battery apparatus according to this embodiment will be describedwith reference to FIG. 2.

[0059]FIG. 2 is a circuit diagram showing the internal structure of thelow order control device used for the battery apparatus according to oneembodiment of the present invention. FIG. 2 shows the structure of thelow order control device IC-1, and the other low order control devicesIC-2, IC-3 have the same structure. Like reference numerals are used toindicate like components to those shown in FIG. 1.

[0060] Switching element drive units Dr1, Dr2, Dr3, Dr4 are respectivelyconnected to control terminals of capacity adjustment switching elementsS1, S2, S3, S4 and drive the respective switching elements S1, S2, S3,S4. The drive units Dr1, Dr2, Dr3, Dr4 each obtain a signal from a logiccircuit 3 within the low order control device IC-1 and drive theswitching elements S1, . . . , S4 separately.

[0061] One end of analog switches AS1, AS2, AS3, AS4 is connected to thepositive electrodes of the battery cells and the other end commonlyconnected to a positive terminal C1P of a capacitor C1. Similarly,analog switches BS1, BS2, BS3, BS4 have their one end connected to thenegative electrodes of the battery cells and the other end commonlyconnected to a negative terminal C1N of the capacitor C1. And, an analogswitch CS1 is connected to the positive terminal C1P of the capacitor C1and the other end of the analog switch CS1 is connected to a positiveterminal C2P of a second capacitor C2. Besides, an analog switch CS2 isconnected to the negative terminal C1N of the capacitor C2 and the otherend of the analog switch CS2 is connected to the negative terminal C2Nof the second capacitor C2.

[0062] The analog switch AS1 and the analog switch BS1 are paired, andalso AS2 and BS2, AS3 and BS3, and AS4 and BS4 are paired respectivelyand turned on or off at the same time. Pair (a) of the analog switch AS1and the analog switch BS1, pair (b) of the analog switch AS2 and theanalog switch BS2, pair (c) of the analog switch AS3 and the analogswitch BS3, and pair (c) of the analog switch AS4 and the analog switchBS4 operate as four multiplexer switches. Specifically, one of thebattery cells VB1, . . . , VB4 is selected by the multiplexer switchesof (a), . . . , (d), and the selected battery cell is connected to thefirst capacitor CS1. Meanwhile, the analog switch CS1 and the analogswitch CS2 are turned on or off simultaneously and, when they are turnedon, the first capacitor CS1 and the second capacitor CS2 are connected.

[0063] It is assumed that the operation mode that the analog switch CS1and the analog switch CS2 are turned on is (e). And, for example, whenthe battery cell VB1 is measured for a voltage, the logic circuit 3alternately repeats a first mode to turn on the pair (a) of the analogswitch AS1 and the analog switch BS1 and a second mode to turn on thepair (e) of the analog switch CS1 and the analog switch CS2. During theabove operation, the multiplexer switches of (b), . . . , (d) are heldoff. The first mode (a) and the second mode (e) are pulse repeated forhundreds of times to finally have the same voltage among the batterycell VB1, the analog switch CS1, and the analog switch CS2. This isbecause when (a) and (b) are performed once, an electric currentcorresponding to a potential difference between the battery cell VB1 andthe analog switch CS1 and between the analog switch CS1 and the analogswitch CS2 flows, and a potential difference is reduced.

[0064] The first mode to turn on the pair (b) of the analog switch AS2and the analog switch BS2 and the second mode to turn on the pair (e) ofthe analog switch CS1 and the analog switch CS2 are alternatelyrepeated, during which the multiplexer switches of (a), (c) and (d) areheld off, and the first mode (b) and the second mode (e) are pulserepeated for hundreds of times. As a result, the battery cell VB2, theanalog switch CS1 and the analog switch CS2 have the same voltage.

[0065] Similarly, the first mode to turn on the pair (c) of the analogswitch AS3 and the analog switch BS3 and the second mode to turn on thepair (e) of the analog switch CS1 and the analog switch CS2 arealternately repeated. As a result, the battery cell VB3, the analogswitch CS1 and the analog switch CS2 have the same voltage.

[0066] And, the first mode to turn on the pair (d) of the analog switchAS4 and the analog switch BS4 and the second mode to turn on the pair(e) of the analog switch CS1 and the analog switch CS2 are alternatelyrepeated. As a result, the battery cell VB4, the analog switch CS1 andthe analog switch CS2 have the same voltage.

[0067] In the figure, the voltage detection circuit indicated by abroken line has a structure including the aforementioned multiplexerswitches, analog switches, and first and second capacitors. Output ofthe voltage detection circuit 1 is a positive voltage (C2P) of theanalog switch CS2. The positive voltage C2P is compared with thereference voltage corresponding to an overcharge voltage, anoverdischarge voltage, a capacity adjustment level or the like bycomparators CMP1, CMP2, CMP3. The reference voltage is supplied from areference power circuit 2. The output (C2P) of the voltage detectioncircuit 1 is transmitted as a detected cell voltage Vx to input of anA/D converter 7, and the analog value of the positive voltage (C2P) ischanged to a digital value by the A/D converter 7. The A/D converter 7can compensate a voltage detection error by the signal given to theaforementioned terminals A1, . . . , A3 and the terminals B1, B2.

[0068] The reference power circuit 2 produces a fixed voltage (e.g., 5V) from the total voltage of the battery cells VB1 to VB4, supplies anelectric current to a reference voltage element VR which is disposedoutside of the low order control device IC-1 to produce a very accuratevoltage than the previous constant voltage and takes the voltage from aterminal Vref-1 into the low order control device IC-1. The voltageinput from the terminal Vref-1 is divided into several kinds ofvoltages, which are then used as the reference voltages according to thecomparators CMP1, CMP2, CMP3. A clock generator 5 produces a clock by anoscillator CZ disposed outside of the low order control device IC-1 anduses it in the logic circuit 3 or the like. Detailed structures of aninput circuit 4 and an output circuit 6 will be described later withreference to FIG. 3 and FIG. 4.

[0069] Then, a first structure of the output circuit 6 and input circuit4 used for the low order control device in the battery apparatusaccording to the embodiment will be described with reference to FIG. 3.

[0070]FIG. 3 is a circuit diagram showing the first structure of theoutput circuit 6 and the input circuit 4 used for the low order controldevice in the battery apparatus according to one embodiment of theinvention. FIG. 3 shows details of the output circuit 6 of the low ordercontrol device IC-1 and the input circuit 4 of the low order controldevice IC-2. Like reference numerals are used to indicate likecomponents to those shown in FIG. 1 and FIG. 2.

[0071] A transistor Q in a power circuit 2 has a base electric currentcontrolled by a power control circuit 8 to output a fixed voltage to aterminal VDD and supplies the fixed voltage to the output circuit 6.

[0072] The output circuit 6 is disposed between the terminal VDD and theGND-1 of the low order control device IC-1 and has a complementaryswitch comprised of P-MOSFET (MP1) and N-MOSFET (MN1). A resistor R14 isconnected between the P-MOSFET (MP1) and the N-MOSFET (MN1). And, theP-MOSFET (MP1) is connected with a resistor R13 in parallel. Output ofthe complementary switch is applied to a gate terminal of P-MOSFET(MP3).

[0073] Here, when the P-MOSFET (MP1) is turned on by a signal outputfrom the logic circuit 3, a short-circuit is caused between the gate andthe source of the P-MOSFET (MP3) to turn off the P-MOSFET (MP3). And,when the N-MOSFET (MN1) is turned on, voltages which are resulted fromthe division of the voltage of the terminal VDD by the resistor R13 andthe resistor R14, and voltages at both ends of the resistor R13 areapplied between the gate and the source of the P-MOSFET (MP3). Thevoltages at both ends of the resistor R13 are set to be larger than agate threshold voltage of the P-MOSFET (MP3) and turn on the P-MOSFET(MP3) but set to be slightly larger than a gate threshold voltage tosuppress an output electric current of the P-MOSFET (MP3) (about 1V or2V higher than a threshold voltage).

[0074] As a result, the P-MOSFET (MP3) operates as a fixed currentswitch and passes the output fixed electric current to the input circuit4 of the low order control device IC-2. An electrostatic breakdownprevention circuit which has a diode D1 and a resistor RE1 connected inseries is disposed between the output terminal of the P-MOSFET (MP) andthe terminal VDD, and when a serge voltage is input from the outside tothe output terminal Out-1, the serge voltage is bypassed to the terminalVDD and a capacitor CV1 connected to the terminal VDD via the resistorRE1 and the diode D1. Thus, the electrostatic breakdown between the gateand the source of the P-MOSFET (MP3) due to the serge voltage can beprevented. And, a resistor RE2 and a diode D2 are also provided betweenthe output terminal and GND-1 of the P-MOSFET (MP3) as measures for anelectrostatic breakdown, and a zener diode ZD1 is additionally connectedin series.

[0075] As shown in the drawing, when I/O terminals of the two low ordercontrol devices IC-1, IC-2 are connected without isolating, an electriccurrent path, which starts from the output terminal Out-1 and returns toGND-1 via the input terminal In-1 and the battery cell connected to thelow order control device IC-2, is formed when P-MOSFET (MP3) is off, andthe battery cell is discharged. When the state is left as it is, thebattery cell is overdischarged. Therefore, the zener diode ZD1 having abreakdown voltage higher than the battery cell voltage is disposed onthe above electric current path to interrupt the discharge current.

[0076] Then, the structure of the input circuit 4 will be described. Theinput terminal In-1 of the low order control device IC-2 is connected tothe negative electrode of the battery cell VB5 through the seriesconnection of a resistor RE4 and a resistor RE6. Therefore, thereference potential of the input terminal In-1 is a negative potentialof the battery cell VB5 higher than GND-2. The gate terminal of N-MOSFET(MN2) is connected to the input terminal In-1 via a resistor RE3, andthe source terminal of N-MOSFET (MN2) is also connected to the negativeelectrode of the battery cell VB5 via the resistor RE6. A diode D3 isdisposed between the gate terminal of the N-MOSFET (MN2) and thepositive electrode of the battery cell VB5, and a diode D4 is disposedbetween the gate terminal and the source terminal of the N-MOSFET (MN2)in order to prevent an electrostatic breakdown. By configuring in thisway, the N-MOSFET (MN2) has a reference potential which becomes anegative potential of the battery cell VB5 higher than the GND-2.

[0077] A resistor RE5 is disposed between the drain terminal of theN-MOSFET (MN2) and the positive electrode of the battery cell VB5, andvoltages at both ends of the resistor 5 are applied between the gate andthe source of the P-MOSFET (MP4). The drain terminal of the P-MOSFET(MN4) is connected to GND-2 through the series connection of resistorsRE7, RE8. And, a zener diode ZD2 is disposed in parallel to the resistorRE8, and voltages at both ends of the resistor RE8 are transmitted tothe logic circuit 3.

[0078] The input circuit 4 configured as described above is a circuitwhich converts a potential in the multiple steps. Specifically, a fixedelectric current output by the P-MOSFET (MP3) of the low order controldevice IC-1 is received by the N-MOSFET (MN2) which has the negativeelectrode of the battery cell VB5 as the potential reference, and whenthe N-MOSFET (MN2) is turned on, the P-MOSFET (MP4) is turned on with avoltage produced in the resistor RE5, and a signal voltage is producedat both ends of the resistor RE8 with an electric current passingthrough the P-MOSFET (MP4) and transmitted to the logic circuit.

[0079] A general circuit, particularly an integrated circuit, has aninput terminal with the ground as the reference potential and an outputterminal. Meanwhile, the low order control device of this embodiment hasoutput connected to a fixed electric current and input connected to areference potential higher than the ground of the circuit and convertsthe potential in the multiple steps by the output circuit. Such aconfiguration is necessary to connect the control devices withoutisolating. The prevention of the discharge of the battery cell by thezener diode ZD1 was described above. And, when the potential standard ofthe input terminal In-1 is selected at the ground GND-2, the batterycells VB5, . . . , VB8 constitute a route which runs to discharge fromthe output terminal Out-1 of the low order control device IC-1 via theinput terminal In-1 of the low order control device IC-2 while theP-MOSFET (MP3) is off. In order to interrupt the discharge current, itis necessary to increase a breakdown voltage of the zener diode. And, asa voltage between the source and the drain of the P-MOSFET (MP3), atotal voltage of the battery cells VB5, . . . , VB8 is applied, so thata voltage stress is always applied to the P-MOSFET (MP3). In view of theabove points, it is desired that the reference potential of the inputterminal In-1 is selected to be high and the breakdown voltage of thezener diode ZD1 is set low so to reduce a voltage stress of the P-MOSFET(MP3).

[0080] As described above, the discharge current route is formed betweenthe output terminal of the low order control device and the batterycells in the battery module on the low potential side. Specifically,between the output terminal Out-1 of the low order control device IC-1and the battery cell VB6 in the battery module (comprised of the batterycells VB5, VB6, VB7, VB8) on the potential side lower than the low ordercontrol device IC-1, there is formed a discharge current routeconnecting the output terminal Out-1 of the low order control deviceIC-1, input terminal In-1 of the low order control device IC-2, theresistor RE3, the diode D4, the positive electrode of the battery cellVB6, the negative electrode of the battery cell VB5, the positiveelectrode of the battery cell VB5, the ground GND-1 of the low ordercontrol device IC-1, the zener diode ZD1, the diode D2, the resistorRE2, and the output terminal Out-1 of the low order control device IC-1.Therefore, this embodiment has interception elements such as the zenerdiode ZD1, the diodes D2, D4 and the like disposed on this dischargecurrent route in order to prevent the discharge of the batteries.

[0081] Then, a second structure example of the output circuit 6 and theinput circuit 4 used for the low order control device in the batteryapparatus according to this embodiment will be described with referenceto FIG. 4.

[0082]FIG. 4 is a circuit diagram showing the second structure exampleof the output circuit 6 and the input circuit 4 used for the low ordercontrol device in the battery apparatus according to one embodiment ofthe invention. FIG. 3 shows the details of the output circuit 6 of thelow order control device IC-1 and the input circuit 4 of the low ordercontrol device IC-2. Like reference numerals are used to denote likecomponents to those shown in FIG. 1, FIG. 2 and FIG. 3.

[0083] The output circuit 6 of the low order control device IC-1 has thesame structure as the output circuit 6 shown in FIG. 3.

[0084] The input circuit 4 of the low order control device IC-2 isdifferent from the input circuit shown in FIG. 3 in the followingpoints. Specifically, the source terminal of P-MOSFET (MP5) is connectedto the input terminal In-1, the gate terminal of the P-MOSFET (MP5) isconnected to the positive electrode of the battery cell VB5. Thus, thereference potential of the input terminal In-1 is selected for thepositive electrode voltage of the battery cell VB5 having the samepotential as the ground GND-1 of the low order control device IC-1.

[0085] The P-MOSFET (MP5) has zener diode ZD3 and resistor RE9 disposedbetween the source and the gate, and the gate voltage is applied to theP-MOSFET (MP5) with the fixed electric current output by the P-MOSFET(MP3) to turn on the P-MOSFET (MP5). The drain terminal of the P-MOSFET(MP5) is connected to the negative electrode of the battery cell VB6 viathe resistor R4 and the zener diode ZD4. Both end voltages of theresistor RE4 are applied as gate-to-source voltages of the N-MOSFET(MN2). The source terminal of the N-MOSFET (MN2) is also connected tothe negative electrode of the battery cell VB6 via the zener diode ZD4.Resistor RE5 is disposed between the drain terminal of the N-MOSFET(MN2) and the positive electrode of the battery cell VB5 to apply bothend voltages of the resistor RE5 between the gate and the source of theP-MOSFET (MP4). The drain terminal of the P-MOSFET (MP4) is connected tothe ground GND-2 through the series connection of the resistors RE7,RE8. Zener diode ZD2 is disposed in parallel to the resistor RE8 totransmit both end voltages of the resistor RE8 to the logic circuit 3.

[0086] According to the above configuration, there is no battery cell onthe route running from the output terminal Out-1 of the low ordercontrol device IC-1 to the ground GND-1 via the input terminal In-1 ofthe low order control device IC-2 and the zener diode ZD3, and there isno need to worry about the discharge current of the battery. There isalso formed a route running from the input terminal In-1 of the loworder control device IC-2 to reach the negative electrode of the batterycell VB6 via the drain and the source of the P-MOSFET (MP5) and thezener diode ZD4 and returning to the ground GND-1 from the battery cellVB6 and the battery cell VB5. When the P-MOSFET (MP3) is off, theP-MOSFET (MP5) is also off, and the battery cells VB5, VB6 do notdischarge over this route. A first element which cuts off the dischargecurrent is the P-MOSFET (MP5), and the zener diode ZD4 is tediously usedto cut off the discharge current, when the P-MOSFET (MP5) is defectiveand flows the discharge current.

[0087] As described above, by configuring as shown in FIG. 3 or FIG. 4,even if the input and output terminals of the low order control deviceare connected without isolating, the discharge current of the batterycell can be cut off, and the non-isolating connection can be made. Inthe examples of FIG. 3 and FIG. 4, the output circuit of the low ordercontrol device IC-1 and the input circuit of the low order controldevice IC-2 are shown by one channel respectively, but they are providedwith the same structure in more than one for a single low order controldevice as shown in FIG. 1.

[0088] Then, a method of controlling the battery apparatus according tothis embodiment will be described with reference to FIG. 5. Here,contents of control to operate the low order control devices IC-1, . . ., IC3 according to the instruction from the high order control deviceMPU in the examples shown in FIG. 1 to FIG. 4 will be described.

[0089]FIG. 5 is a flow chart showing the contents of control of thebattery apparatus according to one embodiment of the invention.

[0090] Here, a flow to make a normal operation after the low ordercontrol devices IC-1, . . . , IC-3, which have been in a sleep mode, areactivated by the signal from the high order control device MPU will bedescribed.

[0091] In step s1, the high order control device MPU transmits anactivation signal to the input terminal In-1 of the low order controldevice IC-1 via the photocoupler F1.

[0092] Then, the input circuit 4 of the low order control device IC-1converts the potential of the signal transmitted to the input terminalIn-1 and transmits the signal to the internal power supply circuit 2 instep s2.

[0093] Then, the internal power supply circuit 2 operates to control thetransistor Q in step s3. It takes time before external capacitor CV1 ofthe low order control device IC-1 is recharged with the output currentof the transistor Q so to have a predetermined voltage VDD.

[0094] Then, when the voltage of the capacitor CV1 reaches a prescribedvalue or higher which is slightly smaller than the voltage VDD in steps4, the logic circuit 3 and also each circuit shown in FIG. 2 areoperated. Then, the voltage of CV1 is controlled to the fixed value VDD.

[0095] Then, the logic circuit 3 recognizes the activation signaltransmitted from the high order control device MPU and transmits it tothe low order control device IC-2 having a potential lower by one rankthrough the output circuit 6 in step s5.

[0096] Similarly, the low order control device IC-2 and the low ordercontrol device IC-3 are operated by the same flow as in the steps s1, .. . , s5. Besides, the low order control device IC-3 returns theactivation signal to the high order control device MPU via thephotocoupler F4.

[0097] Then, the high order control device MPU recognizes that all thelow order control devices IC-1, IC-2, IC-3 are activated from theirsleep mode and proceeds to give the next instructions in step s6.Specifically, the high order control device MPU uses photocouplers F1, .. . , F3 and transmits serial type control instructions to the low ordercontrol devices IC-1, . . . , IC-3.

[0098] Then, the low order control device IC-1 converts the potential ofthe serial signal obtained from the input terminals In-1, . . . , In-3by the input circuit 4 and deciphers by the logic circuit 3 in step s7.And, the signal is temporarily stored in the register, and the sameserial signal is sent to the next low order control device IC-2.

[0099] Subsequently, the low order control devices IC-2, IC-3 alsooperate in the same way as in the step s7. And, the low order controldevice IC-3 uses the photocouplers F4, . . . , F6 to return the serialsignal to the high order control device MPU.

[0100] In step s8, the high order control device MPU checks the returnedserial signal and, if it is normal, sends the next control instructions.Meanwhile, if the serial signal returned to the high order controldevice MPU had an error, the number of errors related to the signaltransmission is multiplied in step s9 and, if it is less than anallowable number of times, the same instruction signal is sent to thelow order control device IC-1 to perform once again. Meanwhile, if thenumber of errors has reached the allowable number of times or more, itis determined as abnormal, and the high order control device MPU outputsan abnormal signal to the high order system in step s10.

[0101] This control flow has a time delay before the instruction reachesfrom the low order control devices IC-1 to IC-3. However, a batteryvoltage change is slower than the operation of the control circuit suchas a microcomputer, and the monitoring of the battery cell conditionperformed by the low order control devices IC-1 to IC-3 may besatisfactory by performing about every tens of ms. Therefore, a timedelay caused in the transmission of the signal from the low ordercontrol devices IC-1 to IC-3 is not a problem if it is smaller than thestate monitoring cycle. Meanwhile, the high order control device MPU cancompare the instruction issued to the low order control device IC-1 withthe one returned from the low order control device IC-3 to find which ofthe low order control devices had an error. Particularly, when a signalis sent without isolating, it is worried that there might be an effectdue to noise produced by an inverter or the like connected to thesecondary battery. But, according to the aforementioned control method,the high order control device MPU can check that each of theinstructions is accurately recognized by all the low order controldevices, and the reliability of the apparatus can be improved.

[0102] With reference to FIG. 6, the control method for the capacityadjustment by the battery apparatus according to this embodiment will bedescribed.

[0103]FIG. 6 is a flow chart showing the contents of control to adjustthe capacity of the battery apparatus according to one embodiment of thepresent invention.

[0104] The high order control device MPU instructs the adjustment ofcapacity to the low order control devices IC-1, IC-2, IC-3 in step s11.

[0105] Then, the low order control devices IC-1, IC-2, IC-3 store theinstructions in the register and send the same instructions to a loworder control device having a potential lower by one level in step s12.This method is the same as the one shown in FIG. 5.

[0106] Then, the high order control device MPU checks the instructionsreturned from the low order control device IC-3 in step s13 and, if theywere normal, proceeds to step s14 but if had an error, returns to steps11 and gives the same instructions again.

[0107] If they were normal in step s14, the high order control deviceMPU sends instructions to the low order control devices IC-1, . . . ,IC-3 to go into sleep mode after the capacity adjustment.

[0108] Then, the high order control device MPU checks the return of theinstructions and gets into the sleep mode in step s15. Then, the loworder control devices IC-1, . . . , IC-3 do not receive any instructionfrom the high order control device MPU and operate in a standalonestate, respectively.

[0109] Specifically, the low order control devices IC-1, . . . , IC-3sequentially detect the voltage of the battery cells placed in thecorresponding battery module by the voltage detecting circuit 1 of FIG.2 and compare the detected value with a judgment level (capacityadjusting reference voltage: a voltage output to the comparator CMP3 bythe reference voltage circuit 2 of FIG. 2) in step s16.

[0110] When the voltage of the battery cells is higher than the judgmentlevel, the switching elements S1, . . . , S12 corresponding to therespective battery cells are turned on in step s17, and the process ofstep s16 is performed again.

[0111] When the voltage of the battery cells becomes lower than thejudgment level, the low order control devices IC-1, . . . , IC-3 checkthat the voltage of the battery cells placed in the correspondingbattery module is lower than the judgment value, turn off the internalpower supply supply 2 disposed in the respective devices and get intothe sleep mode in step s18. In the standalone state, the sequence offalling into the sleep mode of the low order control devices IC-1, . . ., IC-3 connected in series is not decided. Therefore, it is configuredin such a way to prevent disadvantages that an excessive voltage isapplied to the fixed current switch MP3 and the battery cells arelocally discharged in the non-isolated connection of the input/outputbetween the high and low order devices as shown in FIG. 3 and FIG. 4.

[0112] In the above example, the capacity adjusting instructions use acapacity adjusting reference voltage which is previously given to thecomparator CMP3 of FIG. 2. But, any voltage instructed by the high ordercontrol device MPU can be used as a capacity instruction value by usingthe A/D converter shown in FIG. 7. In this case, the judgment level instep s16 is any voltage instructed by the high order control device MPU.This point will be described later with reference to FIG. 7.

[0113] Then, a structure and operation of the A/D converter used for thebattery apparatus according to this embodiment will be described withreference to FIG. 7 to FIG. 10. The A/D converter in this embodiment isprovided with a function to calibrate an error of the voltage detectingunit.

[0114] First, a general structure of the A/D converter used for thebattery apparatus according to this embodiment will be described withreference to FIG. 7 and FIGS. 8A to 8D.

[0115]FIG. 7 is a circuit diagram showing a structure of the A/Dconverter used for the battery apparatus according to one embodiment ofthe present invention. FIG. 8A to FIG. 8D are timing charts of the A/Dconverter used for the battery apparatus according to one embodiment ofthe invention. Like reference numerals are used to indicate likecomponents parts to those shown in FIG. 1.

[0116] As shown in FIG. 1, the A/D converter 7 is provided withcompensation terminals A1, . . . , A3 and compensation terminals B1, B2for compensation of a voltage detection error. Voltage (voltage of C2P)Vx detected by the voltage detecting unit 1 shown in FIG. 2 istransmitted to the positive terminal of a comparator 14 via a switchunit Sx3. Meanwhile, electric current i of the fixed current unit 16 isaccumulated in a capacitor Ci via a switch unit Sx1 which is driven insynchronization with the switch unit Sx3. A total voltage of the voltageof the capacitor Ci and an adjustment voltage (Voffset) output by anamplifier 15 is applied to the negative terminal of the comparator 14and compared with the detected voltage Vx. The capacitor Ci, after thevoltage of the battery cell is measured once, is discharged by adischarge circuit of a switch unit Sx2 driven by a logic inverter 13 anda resistor Ri. Specifically, when the switch unit Sx3 is turned on andthe detected voltage Vx is transmitted to the positive terminal of thecomparator 14, the capacitor Ci has a voltage of zero, and the voltageat the negative terminal of the comparator 14 is equal to the adjustmentvoltage (Voffset). The switch unit Sx2 remains in the off state from thetime when the switch unit Sx1 and the switch unit Sx3 are turned on.Therefore, after the time when the switch unit Sx1 and the switch unitSx3 are turned on, the voltage of the capacitor Ci is integrated withthe electric current i to increase with time.

[0117] Output of the comparator 14 changes from “1” to “0” when avoltage resulting from a sum of the voltage of the capacitor Ci and theadjustment voltage (Voffset) is higher than the voltage Vx of theelectric current to be detected. The A/D converter 7 performsintegration type detection for measuring a duration in which the outputof the comparator 14 changes to “0” from the time when the switch unitSx1 and the switch unit Sx3 are turned on.

[0118] Using the adjustment voltage (Voffset) depends on the relationbetween the battery remaining capacity and voltage. For example, alithium-ion battery using amorphous carbon has a battery cell voltage(open-circuit voltage) of about 2.9 V when the remaining capacity is 0%and an open-circuit voltage is about 4.1 V when the capacity is 100%.For example, the A/D converter 7 is demanded to be able to detect avoltage ranging from 2.9 V to 4.1 V accurately, but a voltage at a timewhen the remaining capacity is 0% or below is excluded from themeasurement. Therefore, a voltage (e.g., 2 V) when the remainingcapacity is 0% or less is selected as an adjustment voltage (Voffset) soto enable to detect a voltage which is equal to or higher than theadjustment voltage with high accuracy. Here, the adjustment voltage is avoltage which is obtained by dividing the value of the reference voltageVref shown in FIG. 2 by resistance Rx1, Rx2 and multiplying the obtainedvalue with the gain of the amplifier 15.

[0119] A duration from the time when the switch unit Sx1 and the switchunit Sx3 are turned on to the time when output of the comparator 14becomes 0 is measured as follows. First, a clock pulse is frequencydivided by the first counter 9. It is assumed that the clock pulse shownin FIG. 8D has a frequency of 10 MHz and counted for 128 for example,and a signal of a half cycle shown in FIG. 8A is produced. The number ofcounts is different depending on whether the compensation terminals A1,. . . , A3 are “1” or “0”, and FIG. 8A to FIG. 8D show an example thatcompensation of ±3 pulses can be made with respect to the standard 128pulses. Details of the compensation will be described later withreference to FIG. 9.

[0120] In FIG. 7, when output of the comparator 14 is 1, an AND circuit11 transmits the pulse which is frequency divided by the first counter 9to the next second counter 10. The second counter 10 counts the outputof the first counter 9 until the output of the comparator 14 becomes 0as shown in FIG. 8C. It is assumed that the voltage of the capacitor Cinot containing the adjustment voltage and falling in a range of 0 V, . .. , 3 V is a full scale, and the number of counts up to 3 V is 128pulses. Features of the second counter 10 include that a shift register12 counts ±1 (or 2) for the result of the second counter 10 depending onthe state that the compensation terminals B1, B2 are “1” or “0” as shownin FIG. 8B. Output of the shift register 12 is digitally compared withthe capacity adjustment level transmitted from the high order controldevice MPU or used in the role of transmitting the output of the shiftregister 12 to the high order control device MPU.

[0121] Here, the compensation by the first counter 9 according to thecompensation terminals A1, . . . , A3 is to compensate the voltage valueof the capacitor Ci which is determined depending on the values of theconstant current i and the capacitor Ci and corresponds to the gaincompensation. Compensation of the second counter 10 by the compensationterminals B1, B2 is to compensate the adjustment voltage which is outputof the amplifier 15 and corresponds to the offset compensation.

[0122] When it is assumed that the clock frequency is 10 MHz, the numberof counts by the first counter 9 is 128 and the number of counts by thesecond counter is 128 in full scale as described above, and it takestime of about 1.1 ms when the battery cell has a voltage of 4 V.Therefore, the number of counts by the first and second counters may bechanged depending on the desired accuracy of voltage detection andmeasurement time.

[0123] The compensation terminals A1, A2, A3, B1, B2 of the A/Dconverter 7 are provided to calibrate the accuracy of the referencevoltage source which is separately provided for the low order controldevices IC-1, . . . , IC-3 which are connected in series. Therefore,errors of the fixed current i, the capacitor Ci and the adjustmentvoltage (Voffset) are previously detected for each of the low ordercontrol devices IC-1, . . . , IC-3, and information “1” or “0” is givento the terminals A1, . . . , A3 and the terminals B1, B2 to compensatesuch errors. This “1” or “0” can be set by connecting the respectiveterminals to the VDD or the GND-1 as described above, and a specialdevice such as a laser trimmer of resistance is not required.

[0124] Then, structures and operations of the first counter 9 and thesecond counter 10 in the A/D converter used for the battery apparatusaccording to this embodiment will be described with reference to FIG. 9and FIG. 10.

[0125]FIG. 9 is a circuit diagram showing the structures of the firstcounter 9 and the second counter 10 in the A/D converter used for thebattery apparatus according to one embodiment of the invention. FIG. 10is a truth table of the A/D converter used for the battery apparatusaccording to one embodiment of the invention. Like reference numeralsare used to indicate like component parts to those shown in FIG. 7.

[0126] The counters 9, 10 shown have a structure corresponding to 128counts. The first counter 9 is provided with flip-flops M1, . . . , M7and inputs output of the respective flip-flops to a compensation logic18. The compensation logic 18 can change the cycle of the frequencydivision by ±3 pulses depending on the states of the compensationterminals A1, . . . , A3. The compensation logic 18 is the truth tableshown in FIG. 10 which is prepared in the form of a logical circuit orsoftware. The cycle that the flip-flops M1, . . . , M7 are cleared isvariable depending on the output of the compensation logic 18, and apulse which has the cycle to the clearness as a half cycle is sent tothe second counter 10 which is comprised of flip-flops N1, . . . , N7.The shift register 12 compensates the output of the flip-flops N1, . . ., N7 by ±1 count (or 2 counts) depending on the states of thecompensation terminals B1, B2 and outputs.

[0127] When it is assumed that a voltage range of the capacitor Ci,which is determined by the comparator 14, is 0, . . . , 3V (0, . . . ,5V in voltage Vx) at full scale, ±1 count compensated by the shiftregister 12 corresponds to ±23.4 mV. And, a pulse width (input pulsewidth of the second counter) which is compensated by the compensationlogic 18 can be compensated by ±2% if it is ±3 pulses to 128 pulses.

[0128] The low order control devices IC-1, IC-2, IC-3 shown in FIG. 1inspect the accuracy of the voltage detecting unit before shipping ofthe products, and evaluate the voltage detection accuracy related to thereference voltage error possessed by the respective products. And, thecompensation terminals A1, . . . , A3 and B1, B2 are used for each loworder control device to calibrate so that the voltage detection accuracyfalls in the allowable range. Thus, it is not necessary to providehigh-cost high precision parts for the reference voltage to achieve bothhigh accuracy and low-cost of the device.

[0129] As described above, the quantity of isolating units can bereduced, and a low-cost control device can be provided according to thisembodiment.

[0130] It is also possible to reduce an influence caused by disturbancesuch as noise and to make the signal transmission with improvedreliability.

[0131] Besides, the high accurate voltage detection can be achieved, andit is possible to make cost reduction.

[0132] Then, the battery apparatus according to another embodiment ofthe invention will be described with reference to FIG. 11.

[0133]FIG. 11 is a circuit diagram showing a general structure of thebattery apparatus according to another embodiment of the invention.

[0134] The battery apparatus according to this embodiment has low ordercontrol devices IC-1, IC-2 and a high order control device housed in acharger package 100. Electric cells VB1 to VB4 and battery cells VB5 toVB8 which configure battery modules are housed in a battery module 101separate from the charger package 100.

[0135] Conventionally, mobile equipment has a control device (equivalentto the low order control devices IC-1, IC-2) for detecting a trouble ofbatteries mounted in a battery module. Meanwhile, a nickel hydrogen orlithium battery used for hybrid electric cars is a high power typebattery which can discharge and recharge an electric current of several,. . . , tens of times of a rated electric current in a short time. Sucha high power type battery is expected to be applied for civilian use(e.g., power tools, cordless cleaners, etc.) other than automobiles. Forexample, a power tool is demanded to have a function to discharge anelectric current of about ten times of a battery rating and to rechargequickly with an electric current of several times of a rated current.When an electric current of about ten times of the battery rating isdischarged, the voltage detecting unit of the control device detects avoltage which is obtained by synthesizing an open-circuit voltage (avoltage when a load is not connected to the battery) related to theremaining capacity of the battery and a dropped portion of the voltagewhich is determined by the product of the internal resistance of thebattery and a large current. When the synthesized voltage drops to anoverdischarge level or less, it is determined as an overdischarge by thedetecting circuit, and the apparatus stops. But, the high power typebattery is free from any trouble in view of safety even if thesynthesized voltage drops to the overdischarge level or less in a shorttime. The power tool is required to have a battery light-weighted andcost reduced. Therefore, if there is no obstacle on safety, the controldevice (such as an IC) related to the protection of the battery isfitted on a charger separate from the battery module to monitor thebattery for its abnormality by only a simple temperature detecting unitsuch as a thermistor when the tool is being used, and if a temperaturearound the battery exceeds an allowable value, an electric current maybe shut off on the side of a battery load such as a motor. The abovebattery uses are taken into consideration in this embodiment.

[0136] In the example shown in FIG. 11, the battery module 101accommodates eight battery cells connected in series. Within the charger100, the two low order control devices IC-1, IC-2 shown in FIG. 2 aredisposed in series. The peripheral equipment of the low order controldevices IC-1, CI-2, namely a capacity adjusting switch, a resistor, aclock oscillator and reference voltage parts, have the same structure asthose shown in FIG. 1. Voltage detection compensating terminals A1, A2,A3, B1, B2 are also the same as in FIG. 1.

[0137] A difference from FIG. 1 is a method of connecting the high ordercontrol device MPU and the low order control devices IC-1, IC-2, and anisolating photocoupler is not used but a potential conversion unit usinga switching element is provided in this embodiment. Specifically, thepotential conversion unit which transmits a signal from the high ordercontrol device MPU to the low order control device IC-1 on the highpotential side are provided with N-MOSFET (MN3), (MN4), (MN5) to which agate signal is input from the high order control device MPU. Theseswitch units are respectively connected to a series resistor comprisingthe resistors r1 and r2, the resistors r3 and r4, and the resistors r5and r6. Here, the resistors r1, r2, r3 have one end connected to thepositive electrode of the battery cell VB1 in the highest potential.Voltages of the resistors r1, r2, r3 are connected to gates of theP-MOSFET (MP6), (MP7), (MP8), and when the N-MOSFET (MN3), (MN4), MN5)are turned on or off, the P-MOSFET (MP6), (MP7), (MP8) are also turnedon or off accordingly. The drain terminals of the P-MOSFET (MP6), (MP7),(MP8) are coupled to the input terminals In-1, In-2, In-3 of the loworder control device IC-1, respectively.

[0138] Similarly, a unit for potential conversion of a signal returningfrom the low order control device IC-2 on the low potential side to thehigh order control device MPU is provided with N-MOSFET (MN6), (MN7),(MN8) of which gates are respectively connected to the output terminalsOut-1, Out-2, Out-3 of the low order control device IC-3, and resistersr7, r8, r9 are connected between the drain terminals of the N-MOSFET(MN6), (MN7), (MN8) and the positive electrode of a control power supply21 (Vcc). And, the voltages of the resistors r7, r8, r9 return to thehigh order control device MPU. The high order control device MPU alsosends a signal to a recharge controlling circuit. Specifically, arecharging circuit is formed of a power MOSFET (MN9) connected to a highvoltage power supply VDC, its driver circuit 22, a backflow diode DFconnected to the power MOSFET (MN9), and a choking coil LF of which oneend is connected to the power MOSFET (MN9). And, an electric currentpassing from the high voltage power supply VDC to the battery module 101via the power MOSFET (MN9) is monitored by a current sensor CT2. Thehigh voltage source VDC is produced by an AC/DC converter 23 which isconnected to a commercial AC power supply, and output of the VDC is usedto produce the control power supply 21 for the high order control deviceMPU by a DC/DC converter 24.

[0139] The respective electrodes of the battery cells placed in thebattery module 101 and the corresponding low order control devices IC-1,IC-2 in the charger 100 are connected via terminals a, . . . , i. Thepositive and negative electrodes of the battery module 101 and thecharger 100 are connected to pass a charging current. The charger 100controls the charging current passing through the power MOSFET (MN9) bya signal output from the high order control device MPU. The low ordercontrol devices IC-1, IC-2 perform the capacity adjustment, which wasdescribed with reference to FIG. 6, during or after the battery module101 is recharged. For the capacity adjustment while recharging, when thebattery module 101 and the charger 100 are connected, a voltage of eachbattery cell is measured by the A/D converters mounted on the low ordercontrol devices IC-1, IC-2, and the measured values are sequentiallysent to the high order control device MPU. The high order control deviceMPU calculates a capacity adjustment level from the voltage of eachbattery cell and transmits to the low order control devices IC-1, IC-2.Then, the low order control devices IC-1, IC-2 perform the capacityadjustment and the detection of overcharging while the charging currentflows. It is to be noted that the operation to get into sleep mode afterthe adjustment described in connection with step s18 of FIG. 6 isomitted.

[0140] As described above, a low-cost control device can be achieved bydecreasing a quantity of isolating units according to this embodiment.

[0141] The signal transmission of which reliability is improved can beattained by reducing the influence by the external interference, such asnoise.

[0142] Besides, the highly accurate voltage detection can be achieved,and the cost reduction can be made.

[0143] The method of controlling the battery apparatus according toanother embodiment of the present invention will be described withreference to FIG. 12A to FIG. 12D.

[0144]FIGS. 12A to 12D are timing charts showing the contents of controlin the battery apparatus according to another embodiment of theinvention. The structure of the battery apparatus used in thisembodiment can be either one shown in FIG. 1 and FIG. 11.

[0145]FIGS. 12A to 12D show a transmitting method of I/O data which issent from the high order control device MPU to the low order controldevice IC-1 or among the low order control devices IC-1, IC-2, IC-3.

[0146] The high order control device MPU transmits the clock signalshown in FIG. 12A and input data (FIG. 12B) in synchronization with theclock signal to the low order control device IC-1 in the highestpotential. And, data input from the high potential side to the lowpotential side is serial transmitted among the low order control devicesIC-1, . . . , IC-3. In other words, the low order control device whichhas received the input clock and input data outputs the same signal withshifting by one clock as shown in FIGS. 12C, 12D.

[0147] Thus, signal delay time between the input and output of thesignal can be shortened. In FIGS. 12B and 12D, OV, UV and 50% ORindicated by the broken line indicate overcharge, overdischarge andcapacity adjustment judging bits. When the input data received from thehigh potential side higher by one level has information on the OV, UVand 50% OR, it is indicated by the solid line in FIG. 12, but if not, itis indicated by the broken line. In the output data, 50% OR is indicatedby the solid line, and it means that there was an battery cell exceedingthe capacity adjustment level as the result of detecting the voltage ofthe battery cells (e.g., the battery cells VB1, . . . , VB4) to whichthe low order control device having received the input data corresponds.Thus, the low order control device takes logical add (OR) of the datainput about the overcharge, overdischarge and capacity adjustmentjudgment and the detected result of the corresponding battery cells, andtransmits the result to the low order control device.

[0148] The high order control device MPU can check that at least oneamong all the battery cells exceeds the judgment level if the returneddata had any flag of the OV, UV, 50% OR stood.

[0149] By having the aforementioned serial signal, when the plural loworder control devices are connected without isolating, a signaltransmission delay is short, and a fail safe type is provided by virtueof the OR form, and reliability is improved. When a logical product isused instead of the logical add, the variation in battery voltage can bepresumed from the analysis of a signal when recharging or discharging,and the capacity adjusting function can be operated according to thedetected result.

[0150] In the embodiments shown in FIG. 1 to FIGS. 12A to 12D, thebattery cells VB1, . . . , VB12 are assumed to be the secondarybatteries, but they are not limitative and may be an ultra capacitor.

[0151] According to the present invention, a quantity of isolating unitsis decreased, and the cost reduction of the control device can be made.

[0152] And, the influence by the external interference such as noise isreduced, and the signal transmission with reliability improved can berealized.

[0153] Besides, highly accurate voltage detection can be achieved, andthe cost reduction can be made.

[0154] It should be further understood by those skilled in the art thatthe foregoing description has been made on embodiments of the inventionand that various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and scope of theappended claims.

What is claimed is:
 1. A battery apparatus, comprising: plural batterymodules connected in series each having plural battery cells connectedin series; plural low order control devices which are provided incorrespondence with the plural battery modules, respectively, each ofthe plural low order control devices controlling the plural batterycells configuring corresponding one of the plural battery modules; ahigh order control device which controls the plural low order controldevices; isolating or potential converting units which connects an inputterminal of the low order control device at a highest potential amongthe plural low order control devices, an output terminal of the loworder control device at a lowest potential among the plural low ordercontrol devices, and the high order control device; and interruptionelements each of which is disposed between the output terminal ofcorresponding one of the plural low order control devices and thebattery cell in corresponding one of the plural battery modules on a lowpotential side and blocks discharge current of the battery cells in thecorresponding battery module, wherein terminals related to input andoutput of a signal are connected in an electrically non-isolated stateamong the plural low order control devices.
 2. A battery apparatusaccording to claim 1, wherein the input terminal of each of the plurallow order control devices is electrically connected to the battery cellon a high potential side among the battery cells within thecorresponding battery module being controlled by the low order controldevice.
 3. A battery apparatus according to claim 1, wherein the plurallow order control devices, the isolating or potential conversion unitswhich are disposed on the low order control devices in the highest andlowest potentials, and the high order control device are mounted on asame package, and power is supplied from outside of the package to thehigh order control device.
 4. A control method of a battery apparatuswhich comprises: plural battery modules connected in series each havingplural battery cells connected in series; plural low order controldevices which are provided in correspondence with the plural batterymodules, respectively, each of the plural low order control devicescontrolling the plural battery cells configuring corresponding one ofthe plural battery modules; and a high order control device whichcontrols the plural low order control devices, the control methodcomprising the step of: comparing by the high order control device asignal transmitted to the low order control device at a highestpotential and a signal returning from the low order control device atthe lowest potential, and transmitting a next instruction when thebattery apparatus is determined to be normal.
 5. A control method of abattery apparatus according to claim 4, further comprising the steps of:by one of the plural low order control devices, detecting states of theplural battery cells of the corresponding battery module controlled bythe one low order control device, obtaining a logical add or a logicalproduct of a signal representing the detected states and an input signaltransmitted from the low order control device at a higher potentialamong the plural low order control devices, and outputting a result ofthe logical add or product to the low order control device at a lowerpotential side among the plural low order control devices; and checkingabnormality of the battery apparatus by the high order control deviceaccording to the signal returning from the low order control device atthe lowest potential.
 6. A control method of a battery apparatusaccording to claim 4, wherein the low order control device performscapacity adjustment to discharge remaining capacity of one of thebattery cells in the corresponding battery module which voltage ishigher than a reference value, and the low order control device havingcompleted the capacity adjustment is placed into a sleep mode.
 7. Abattery apparatus, comprising: plural battery modules connected inseries each having plural battery cells connected in series; plural loworder control devices which are provided in correspondence with theplural battery modules, respectively, each of the plural low ordercontrol devices controlling the plural battery cells configuringcorresponding one of the plural battery modules; a high order controldevice which controls the plural low order control devices; a voltagedetecting unit which detects voltages of the plural battery cells withinthe battery module; and an error calibration terminal which calibratesan error of the voltage detecting unit.
 8. A battery apparatus accordingto claim 7, wherein: the voltage detecting unit is an A/D converter; andthe low order control device compensates an output value of the A/Dconverter by previously giving a digital value to the error calibrationterminal of the A/D converter.
 9. A battery apparatus according to claim8, wherein: the A/D converter comprises: an integration unit whichintegrates a unit amount of electricity according to a number of pulses;a comparing unit which compares an integral value of the integrationunit with a voltage of the battery cell and stops the pulse; a counterunit which outputs the number of pulses when the pulse is stopped by thecomparing unit; and a compensation unit which compensates an output ofthe counter unit according to the digital value given to the errorcalibration terminal.
 10. A battery apparatus according to claim 9,wherein the compensation unit changes a counted value of the counterunit according to the digital value given to the error calibrationterminal to compensate an offset of the A/D conversion and changes awidth of the pulse to compensate a gain of the A/D conversion.